Does anyone know if it is possible and how, in Office365 to have POP3/IMAP enabled, but specifically disallow syncing Office365 mailboxes with GMail.

The specific scenario is that the company is a healthcare organization, and we have several users that despite being informed that they are not allowed to use gmail with the company email account they continue. We need to "block" GMail's servers from syncing with all accounts.

Any Ideas?

1 Answer 1



Block POP3 and IMAP. If your business requirements are that data is not allowed to go into Gmail, they probably don't understand that POP and IMAP are equally large holes in their data governance strategy.

Alternatively (or in-addition),

IF you are using federated authentication, you can block auth attempts from the GMail IP range(s) to effectively shut down GMail authentication into O365. Users would then probably figure out how to use App Passwords to bypass this.


You're in a regulated industry. While I agree that you need a technical solution to at least catch when this is happening if not block it outright, you really need the policy to be enforced through the 'people side' of things. Report users who are violating policy, and let your Compliance team sort out the rest.

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